New research questions their safety, but experts say they emit extremely low levels of radiation. Here are the facts.

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Tuesday, March 22 — Full-body scanners that use X-ray technology are under fire this week after articles published in the journal Radiology debated their safety. In one article, the author estimated that there could be 100 extra cancers per year in a population exposed annually to a billion airport security scans.

But the individual cancer risk to any one person is so small that the scans can be considered safe, author David Brenner, PhD, of the Center for Radiological Research at Columbia University Medical Center in New York City said in the article.

So should you opt out of these scans next time you fly? Here’s what you need to know:

How Do Full-Body Airport Scanners Work?

Since 2007, the U.S. Transportation Security Administration (TSA) has rolled out two types of full-body scanners — backscatter X-ray and millimeter-wave devices – at airports in the United States (both types are also used in Canada, England, France, and the Netherlands). There are currently 486 of these devices in use at 78 airports across the United States; about half are backscatter X-ray and half are millimeter wave. (See a list of all the airports that use them here.)

The millimeter wave full-body device relies on radiofrequency waves, which are not radioactive, to scan the body, while backscatter technology uses very low-energy X-rays, to form an image. X-rays are a form of ionizing radiation, which can increase cancer risk when delivered in high-enough doses.

To determine which full-body scanner your airport uses, look at the color and shape of the device. Backscatter scanners (made by Rapiscan) are bluish boxes, while millimeter wave scanners are grey cylinders.

How Much Radiation Do Backscatter Scanners Give Off?

According to the Federal Aviation Administration, one scan emits about 0.0001 millisieverts (mSv) of radiation. To put that number in perspective, that’s about the amount of radiation found naturally in a banana. And you’re exposed to far more radiation from cosmic rays in the atmosphere during a plane flight than you will get during a scan before you board a plane. The radiation exposure from a backscatter device is equivalent to the amount of radiation you’re exposed to in just two minutes of flight time, according to the TSA.

Also, keep in mind that all types of radiation are not created equally. “The radiation from these scanners is different from the kind in medical X-rays,” says James Thrall, MD, president of the American College of Radiology. “It doesn’t penetrate as deeply into your body tissues [as do medical x-rays], so you don’t absorb as much [radiation].”

Can Backscatter Airport Scanners Cause Cancer?

There is a slightly increased cancer risk, but it’s extremely small. There’s about a one in 10 million chance any single person would develop cancer as a result of the radiation they’re exposed to from a single trip involving two scans, Dr. Brenner wrote in the paper in Radiology.

Because the dose of radiation from backscatter full-body scanners is so low, the FDA does not recommend limiting the number of scans a person should receive each year.

Traveling frequently does potentially expose you to more radiation from scanners, but the total amount is still extremely low. A pilot or a flight attendant who gets 240 to 380 scans a year will receive about 0.3 mSV of radiation, Brenner estimated, equivalent to the amount in a mammogram. A frequent flier could receive about 0.2 mSv, or about the amount you’re exposed to annually simply from living at sea level.

For pregnant women and children, it’s natural to be more concerned, because fetuses and children are more vulnerable to health issues from radiation than adults. But experts say the risk is still negligible. “If you’re comfortable with the amount of radiation you’re exposed to while flying, then the tiny additional amount you receive during the scan shouldn’t be a concern,” says Dr. Thrall.

If you’re still nervous about radiation exposure from airport scanners, then you can always opt out of the backscatter scan and ask instead for a pat-down, in which a TSA officer performs a manual check of your body for unsafe items.

"As someone who travels just occasionally, I would have no hesitation in going through the X-ray backscatter scanner," Brenner said in a press release. "Super frequent fliers or airline personnel, who might go through the machine several hundred times each year, might wish to opt for pat-downs. The more scans you have, the more your risks may go up — but the individual risks are always going to be very, very small."

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